Geological Hazard

Indian subcontinent is prone for various natural hazards. Landslide and earthquake are the major geological hazard effecting our country. Remote sensing is essentially used in post disaster scenario to understand the impact and spatial disposition of the damage. Assessment of the geological disasters such as landslide, earthquake and volcanic eruption.

Landslides

In India, in terms of frequency of occurrence, landslides are the most prominent Geohazard causing damage to property, infrastructure and above all; loss of precious lives, almost every year. Nearly 15% of the Indian land area is prone to landslide hazard (GSI, http://www.portal.gsi.gov.in). The Himalayan terrain accounts for about 80% of this, followed by the NE hills, Eastern and Western Ghats, Nilgiri Hills and Ranchi Plateau.

Geospatial techniques have widely been used in the preparation of landslide inventory, landslide hazard and risk assessment, for damage assessment and also for generating early warning. Landslide hazard of an area can be assessed using statistical/geo-technical models or using ANN, SVM etc. Statistical methods are suitable for medium scale (~1:50,000 ) application where as the geo-technical method is data-extensive and is applicable on large scale (~1:5K or larger) and for small areas. The Case Study here describes a multivariate statistical approach for preparing landslide hazard zonation maps in the Himalayan terrain. Using remote sensing data, landslide inventory is generated annually and also after major triggering events [recent studies are Okhimath landslides (14/09/2012) and Sikkim landslides (21/09/2012)]. Landslide hazard zonation (LHZ) and inventory mapping along important tourist and pilgrim routes in the Himalayas is carried out. Recently for the Uttarakhand disaster, the chain of events that led to the massive damage in Kedarnath area has been reconstructed. Landslide inventory mapping was also carried for the entire area. Landslide hazard zonation (2001) and event-based inventory (2013) around Kedarnath.

Earth Quakes

In India, the very high to high seismic hazard zones (Zone V and IV) fall mostly in the Himalaya, NE & Assam, Kutch, Saharanpur-Alwar-Moradabad belt including Delhi and Koyna region. The Lakshadweep and Andaman & Nicobar islands are also in the high seismic hazard zones. The central India is in the moderate to low seismic risk zones. The application of remote sensing technology in earthquake hazard evaluation is mostly in the mapping of active faults and in displacement monitoring using Synthetic Aperture Radar Interferometry technique. In the post-disaster phase, the remote sensing application is basically for damage assessment, where high resolution data aids in rapid evaluation of the destruction during an earthquake

Volcanoes

Volcanism is another geological hazard. Thermal remote sensing can be utilized for monitoring the temperature variations in known, dormant or active volcanic terrains. Remote sensing data can also be used for mapping the extent of volcanic ash deposits and lava flow extent, post disaster. The barren island volcano is an active volcano in India and has been studied using remote sensing data.

Geological Hazard